.\" -*- nroff -*-
.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
.\" Copyright 2010-2014 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" Copyright (c) 2020      Google, LLC. All rights reserved.
.\" $COPYRIGHT$
.TH MPI_Type_indexed 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fBMPI_Type_indexed, MPI_Type_create_hindexed\fP \- Creates an indexed datatype.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Type_indexed(int \fIcount\fP, const int\fI array_of_blocklengths[]\fP,
	const int\fI array_of_displacements[]\fP, MPI_Datatype\fI oldtype\fP,
	MPI_Datatype\fI *newtype\fP)

int MPI_Type_create_hindexed(int \fIcount\fP,
	const int\fI array_of_blocklengths[]\fP,
	const MPI_Aint\fI array_of_displacements[]\fP, MPI_Datatype\fI oldtype\fP,
	MPI_Datatype\fI *newtype\fP)

.fi
.SH Fortran Syntax
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_INDEXED(\fICOUNT, ARRAY_OF_BLOCKLENGTHS,
		ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR\fP)
	INTEGER	\fICOUNT, ARRAY_OF_BLOCKLENGTHS(*)\fP
	INTEGER	\fIARRAY_OF_DISPLACEMENTS(*), OLDTYPE, NEWTYPE\fP
	INTEGER	\fIIERROR\fP

MPI_TYPE_CREATE_HINDEXED(\fICOUNT, ARRAY_OF_BLOCKLENGTHS,
		ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR\fP)
	INTEGER	\fICOUNT, ARRAY_OF_BLOCKLENGTHS(*)\fP
	INTEGER	\fIOLDTYPE, NEWTYPE\fP
	INTEGER(KIND=MPI_ADDRESS_KIND) \fIARRAY_OF_DISPLACEMENTS(*)\fP
	INTEGER	\fIIERROR\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Type_indexed(\fIcount\fP, \fIarray_of_blocklengths\fP, \fIarray_of_displacements\fP,
		\fIoldtype\fP, \fInewtype\fP, \fIierror\fP)
	INTEGER, INTENT(IN) :: \fIcount\fP, \fIarray_of_blocklengths(count),\fP
	\fIarray_of_displacements(count)\fP
	TYPE(MPI_Datatype), INTENT(IN) :: \fIoldtype\fP
	TYPE(MPI_Datatype), INTENT(OUT) :: \fInewtype\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

MPI_Type_create_hindexed(\fIcount\fP, \fIarray_of_blocklengths\fP,
		\fIarray_of_displacements\fP, \fIoldtype\fP, \fInewtype\fP, \fIierror\fP)
	INTEGER, INTENT(IN) :: \fIcount\fP, \fIarray_of_blocklengths(count)\fP
	INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) ::
	\fIarray_of_displacements(count)\fP
	TYPE(MPI_Datatype), INTENT(IN) :: \fIoldtype\fP
	TYPE(MPI_Datatype), INTENT(OUT) :: \fInewtype\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
count
Number of blocks -- also number of entries in array_of_displacements and
array_of_blocklengths (nonnegative integer).
.TP 1i
array_of_blocklengths
Number of elements per block (array of nonnegative integers).
.TP 1i
array_of_displacements
Displacement for each block, in multiples of oldtype extent for MPI_Type_indexed and bytes for MPI_Type_create_hindexed (array of
integer for
.BR MPI_TYPE_INDEXED ,
array of
.I MPI_Aint
for
.BR MPI_TYPE_CREATE_HINDEXED ).
.TP 1i
oldtype
Old datatype (handle).
.sp
.SH OUTPUT PARAMETERS
.ft R
.TP 1i
newtype
New datatype (handle).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
The function MPI_Type_indexed allows replication of an old datatype into a sequence of blocks (each block is a concatenation of the old datatype), where each block can contain a different number of copies and have a different displacement. All block displacements are multiples of the old data type's extent.
.sp

\fBExample:\fP Let oldtype have type map {(double, 0), (char, 8)}, with extent 16. Let  B = (3, 1) and let D = (4, 0).  A call to MPI_Type_indexed(2, B, D, oldtype, newtype) returns a datatype with type map
.sp
.nf
    {(double, 64), (char, 72), (double, 80), (char, 88),
    (double, 96), (char, 104),
    (double, 0), (char, 8)}
.fi
.sp
That is, three copies of the old type starting at displacement 4 x 16 = 64, and one copy starting at displacement 0.
.sp
In general, assume that oldtype has type map
.sp
.nf
    {(type(0), disp(0)), ..., (type(n-1), disp(n-1))},
.fi
.sp
with extent ex. Let B be the array_of_blocklength argument and D be the
array_of_displacements argument. The newly created datatype has
.br
.nf
n x S ^count-1
    i = 0           B[i]  entries:

    {(type(0), disp(0) + D[0]* ex), ...,
    (type(n-1), disp(n-1) + D[0]* ex), ...,
    (type(0), disp(0) + (D[0] + B[0]-1)* ex), ...,
    (type(n-1), disp(n-1) + (D[0]+ B[0]-1)* ex), ...,
    (type(0), disp(0) + D[count-1]* ex), ...,
    (type(n-1), disp(n-1) + D[count-1]* ex), ...,
    (type(0), disp(0) +  (D[count-1] + B[count-1] -1)* ex), ...,
    (type(n-1), disp(n-1) + (D[count-1] + B[count-1] -1)* ex)}
.fi
.sp
A call to MPI_Type_vector(count, blocklength, stride, oldtype, newtype) is equivalent to a call to MPI_Type_indexed(count, B, D, oldtype, newtype) where
.sp
.nf
    D[j] = j * stride, j = 0,..., count-1

and

    B[j] = blocklength, j = 0, .., count-1
.fi

The function MPI_Type_create_hindexed is identical to MPI_Type_indexed, except that block displacements in \fIarray_of_displacements\fP are specified in bytes, rather than in multiples of the \fIoldtype\fP extent.

.SH ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

.SH SEE ALSO
.ft R
.sp
MPI_Type_hindexed
.br

